Beyond price and features, the main difference between virtualization products is the technique used to perform the virtualization. On the server virtualization front, there are two main techniques: Native virtualization and paravirtualization. Native virtualization virtualizes all of the hardware that runs under a guest virtual machine, so that the guests can run an unmodified operating system. Paravirtualization is a technique that sends virtualization sensitive operations straight to the virtual machine monitor. Since this is accomplished by running the virtual machine monitor in ring0 of the processor, the guest operating systems cannot normally run without modification. Newer virtualization enabled processors such as Intel VT and AMD-V enabled processors will allow guest virtual machines to run unmodified on paravirtualization platforms.
"Higher level virtualization" refers to an operating system, which is a virtualization technique that partitions a single operating system into several virtual environments. The most well-know product for operating system virtualization is SWSoft's Virtuozzo. This is called "higher level virtualization" because it runs in a higher layer (the operating system) than traditional server virtualization techniques.
VARs should be aware of operating system virtualization because it offers customers with high-end application or database servers an incentive to explore virtualization. Application and database servers usually need to take advantage of the majority of processing power available on the physical host. This may not make traditional server virtualization techniques very feasible. If a VAR is aware of all the alternatives for virtualization, it can offer alternative services to its clients.
This was first published in May 2007